Bioprospecting Antibacterial Properties of Fungi Isolated from Kakinada Sea Coast and Eucalyptus Foliage

Abstract

Fungi produce a wide range of secondary metabolites with bactericidal or bacteriostatic properties. In search of novel antibacterial compounds recently, many fungi of marine and plant origin have been studied for their antimicrobial properties. This work aimed to study bio-prospect marine and endophytic fungi for their antibacterial properties. To determine the antibacterial properties of ethyl acetate extracts of fungal isolates. Intensive microbiological methods were followed for isolation, differential growth, and qualitative screening of enzyme production. The isolates were characterised and identified based on morpho-taxonomy, 18S rRNA gene sequencing, and phylogenetic analysis of the tar-get genes. The antimicrobial activity of fungal ethyl acetate extracts against S. aureus, B. sub-tilis, and E. coli was evaluated using a well-diffusion method, and MIC was determined by the microdilution method. Cell lysis was observed through Transmission Electron Microscopy. A BLAST search of 18S rRNA gene sequences of the marine isolates GSBT S13 and GSBT S14 showed 99.3 % sequence similarity with A. glaucus for both isolates and that of endophyte GSBT E3 showed 99.7 % sequence similarity with B. pinkertoniae. Cellulase pro-duction was comparatively higher in GSBT E3 and lipase from GSBT S13 and GSBT S14. Ethyl acetate extracts of GSBT S14 and GSBT E3 showed a clear zone of inhibition by the well-diffusion method, further confirmed by electron microscopy. HR-TEM showed that the ethyl acetate extracts of the isolates appeared to damage the cell membrane, leading to cell shrinkage and death in E. coli and S. aureus. GSBT S13 and GSBT S14 exhibited extracellular amylase, cellulase, and lipase activities. Ethyl acetate extracts of both GSBT S14 and B. pinkertoniae GSBT E3 showed better antibacterial properties against S. aureus.